Question: If $x \triangleright y = 7x+y$ and $x \triangleleft y = xy+4x-y$, find $0 \triangleright (5 \triangleleft -1)$.
Answer: First, find $5 \triangleleft -1$ $ 5 \triangleleft -1 = (5)(-1)+(4)(5)-(-1)$ $ \hphantom{5 \triangleleft -1} = 16$ Now, find $0 \triangleright 16$ $ 0 \triangleright 16 = (7)(0)+16$ $ \hphantom{0 \triangleright 16} = 16$.